Microbial contamination of dental unit water recently has been recognized as a serious health concern. Dental unit water systems provide an environment conducive to the growth of a variety of microorganisms. Many dental units provide water from a water reservoir. This water passes through narrow tubes and then into a patient's mouth during treatment. Patients are exposed to the water during rinsing procedures and may also ingest small amounts during treatment. The water is typically stored at room temperature or heated slightly. The characteristic low flow-rates, warm temperatures, and high ratios of surface-area-to-volume all promote microbial growth.
The health effects of exposure to microbial contamination from dental unit water systems have not been determined. It is well known, however, that contamination of drinking water can have adverse health consequences. While dental unit water is not consumed in large quantities, its use may be a factor when such consequences arise. The risks are especially acute for people with compromised immune systems. Plus, even patients who would not be affected by contaminated water may prefer to be treated with disinfected water. Clearly, efforts to disinfect dental unit water systems are warranted.
Contamination of dental unit water systems occurs within the water itself and on surfaces exposed to the water. These types of contamination are related, because microbes from the surfaces are introduced into the water and microbes from the water adhere to the surfaces. In general, the microbial concentrations will be much greater on the surfaces than in the water. Many types of microbes purposefully anchor themselves to solid surfaces by excreting a sticky polysaccharide material. This anchoring process is done in order to facilitate propagation. The surface propagation of these organisms is difficult to avoid. Once some microbes have become anchored to a surface, colonies will begin to form. Eventually, the surfaces will become coated with a layer of biological material referred to as a “biofilm.”
Biofilms are especially difficult to remove from the surfaces within dental units that cannot be exposed and cleaned manually (e.g., the inner surface of tubing). Passing a disinfecting fluid through the system will not necessarily destroy the biofilm, in part because some microbes are shielded by the constituent polysaccharide material and/or other microbes.
Several products have been developed in an effort to remove biofilms from dental unit water systems. These products use certain compounds to penetrate the biofilms and expose them to antimicrobial agents. Such products include Ultra®, which is manufactured by the Sterilex Corporation and Dentacide®, which is manufactured by Frio Technologies. Most of these products are designed to be introduced into the system overnight and flushed in the morning. They are not designed for continuous daily use and/or patient treatment use. These “shock products” are often slightly toxic and would be unpleasant and/or harmful if ingested by patients. Periodic disinfection of the system with shock products is time consuming and inadequate. There is a need for compositions directed to the sustained disinfection of dental unit water and the inhibition of biofilm growth.
Conventional compositions for disinfecting dental unit water have included a variety of compounds. For example, U.S. Pat. No. 6,544,427 discloses the use of colloidal silver and U.S. Pat. No. 6,419,850 discloses the use of EDTA, benzalkonium chloride, and sodium tosylchloramide. In addition to disinfecting compositions, conventional disinfecting methods and devices include, among others, in-line filtration and purge systems.
Conventional compositions, methods, and devices are all deficient in at least one significant respect. For example, some conventional compositions include only one class of antimicrobial agent. These compositions have diminished antimicrobial effectiveness because some organisms may be resistant to that particular class of antimicrobial agent.
There is a need for improved compositions, methods, and devices for the disinfection of dental unit water.